Separation and purification of pyrroloquinoline quinone from Gluconobacter oxydans fermentation broth using supramolecular solvent complex extraction

In this paper, new supramolecular extractants, which contained surfactant, alkane and alkanol, were designed and used to separate PQQ. After a series of tests, the optimal extractant composition was determined as benzalkalonium (C8-C16) chloride (BC): n-hexane:n-pentanol, and the highest extraction rate could reach 98%. The extraction equilibrium could be reached in five minutes. The mechanism of the extraction selectivity was inferred as an ion-pair and π-π complexation interaction between PQQ and BC, which was indicated by UV and fluorescence quenching experiments. To recycle the organic extractant, the extract was back-extracted with sodium chloride solution. After extraction, back extraction and crystallization, an isolated product with a purity of 97.5% was obtained from G. oxydans fermentation broth. The product was identified as PQQ by HPLC analysis and MS. Above all, the present research developed a simple and efficient method for the separation of PQQ from fermentation broth.